Cochlear Implant Electrode Stimulation via Speech Zero-Crossing Mapping
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Solution Overview
Problem
Current cochlear implant speech coding strategies based on the 'place principle' fail to provide instantaneous and continuous information to the auditory nerves, especially in noisy environments, and are ineffective for complex tones, leading to poor speech perception and machine-like sound quality.
Innovation Solution
A new speech strategy that utilizes the time duration between zero crossings of the speech signal to activate electrodes inside the cochlea, mapping temporal segment durations to spatial locations along the basilar membrane, providing instantaneous and continuous information about the speech signal, and using the mechanical motion of the oval window to stimulate the auditory nerve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral band mapping to electrodes is used based on place principle, then frequency discrimination is achieved, but instantaneous and continuous information is not provided to auditory nerves
Solution Approach 1:
The patent changes the parameter used for electrode activation from spectral frequency bands to temporal zero-crossing intervals. By measuring the time duration between zero-crossings of the speech waveform and mapping these temporal intervals to electrode positions, the system provides instantaneous information about the speech signal while maintaining frequency discrimination capability through the temporal characteristics of the waveform.
2Productivity
If spectral information is used to activate electrodes, then speech coding is achieved, but performance drops dramatically in noisy environments
Solution Approach 1:
The patent extracts only the zero-crossing points and their temporal intervals from the speech signal, discarding the complex spectral analysis. This simplified extraction method focuses on the fundamental temporal structure of speech that remains robust in noisy environments, eliminating the vulnerability to noise that plagues spectral-based methods.
3Ease of operation
If place principle mapping is used for complex tones, then electrode activation is achieved, but basilar membrane vibration does not follow place principle for complex signals
Solution Approach 1:
Instead of mapping frequency content to spatial locations as in the place principle, the patent inverts the approach by mapping temporal duration intervals to spatial electrode positions. This inversion aligns with the actual mechanical response of the basilar membrane to complex tones, where the temporal waveform characteristics directly influence the vibration pattern rather than pure frequency-place mapping.
4Measurement precision
If Fast Fourier Transform and multiple band-pass filters are used, then spectral analysis is achieved, but processing complexity and hardware requirements increase
Solution Approach 1:
The patent extracts only the zero-crossing points from the speech waveform, requiring no FFT calculations or multiple band-pass filters. This minimal extraction approach dramatically simplifies the processing architecture while capturing the essential temporal information needed for effective speech coding and electrode activation.
Data Source
AI summary
The present invention provides a method implementing a speech strategy based on zero crossing behavior of speech time waveforms; the zero crossing containing both spectral and temporal speech information. This method uses temporal information of speech to activate electrodes instead of spectral information; maps temporal segment durations to spatial durations along the basilar membrane inside the cochlea; and provides instantaneous, continuous information about speech to electrodes that stimulate the auditory nerve. Timing of oval window mechanical motion is represented by zero crossings which are used to activate electrodes implanted inside the cochlea. Motion of the tympanic membrane, and the oval and round windows, follow the speech signal temporal waveform. Positive segments of the temporal waveform cause inward displacement of the oval membrane from its stationary position and negative segments causes outward retraction of the membranes. Temporal waveform zero-crossings indicate time instants when the membranes are in their stationary positions.